I've found that no one emails any more. If I want to keep in contact with my friends I need to be on Facebook whether I like it or not.
Thing is though, I do like it most of the time so it's not a problem.
Whoever said about the satisfaction of trimming through your friends list every now and then, is definitely right. I don't know how many times I've done it, but far too many. I don't mind making new friends, as right now I see this as networking. I often share things such as my creations and other things that I make etc on Facebook, and I always wonder if people will see the work and then share it around. I've actually scored paid work through a friend of a friend on Facebook before, to give you an example.
If I accept the add from said random person though and they turn out to be a moronic dreg, then i'll just delete them.
My main sections of contacts are the Admin and moderation team of a website I help moderate, school friends that I still talk to, people from uni, members of an organisation I belong with, and then just my general real life friends
One thing I do do on Facebook is I delete unwanted things from my wall every couple of days. I have no massive backlog of ****, telling people I've commented on someones picture or something, I just take it all off and keep it trim. Sometimes the things I say don't need to be read in a months time by some random person scanning my wall.
I don't do IM anymore either, so really I just check Facebook maybe once or twice a day, maybe more if I am posting up work of mine or just making a status and reading replies. More time is spent on forums though. I do know I should knock back on both Facebook and Forums though, just doesn't always happen.